Carbs no more

[Chopper Doc Junior]

http://www.pprune.org/forums/showthread.php?t=299007


Looks like due to the increased cost of insurance against litigation in the US precision airmotive will no longer manufacture carbs. I hope Robinson are thinking about what they are going to do next.

[Bravo73]

They will either:

a) Stop manufacturing carburettored aircraft. (Which they still make a considerable profit on.)

Or

b) They will find a new supplier.



Which do you think they will do?



(PS They will not choose Option c) Recertify the R22 with an injected engine.) :ok:

[heli-mad]

Fuel injected R22......sounds nice, why is so difficult for Mr Robinson to do it i am not 100% sure. We have the 44 ravenII which has been a success story, the cost of certifying an injected engine for the 22 must worth the trouble:confused:
Other manufactures have done it i.e Schweizer 300 (formerly Hughes 300)
Wishful thinking you might say.........

[Jeff Hall]

Are these Carbs OE equipment on a new Lycoming/Robinson then?

If no other manufacturer comes forward then its not just the R22 line that will need modification?
The R44 Raven I continues in series manufacture and is a very successful helicopter - that too would surely need a change?

FI has got to be the way forward, get rid of the carb heat lever and eventually we might even get to the level of single lever and Lambda fuel/air mixture control!

[Bravo73]

the cost of certifying an injected engine for the 22 must worth the trouble:confused:

Nope. The cost (and hassle) of recertifying the R22 far outweigh the benefits. If that was the only option and if the popular rumours are to be believed, Mr Robinson would rather just shut down the R22 production line.



Wishful thinking you might say.........

Wishful indeed! More 'pie in the sky', I'm afraid... :ok:

[Dolmangar]

Bravo73,
I'm just a PPL(H), so excuse my ignorance of aircraft certification. I understand some of the implications as my father spent 30+ years working for P&W.

What order of magnatude are we talking about here for certifying a fuel injected engine? I lurk here but rarely post because I don't have much to add but I'm quite interested in why (besides cost and low volume) that the aviation industry is still using very low tech engines.

Low tech often equals little to go wrong/proven technology. And I gather that most people thought that everything would have been switched to turbine engines long ago (if asked long ago).

Is this simply a case of the industry assuming that there was no future in recipricating engines and stagnating? Or is the certification process overly complicated and costly? (Both maybe?)

The risks for a single engine aircraft engine failure are ofcourse a large consideration, but surely FI engines have been around for several decades and often (at least in the automotive world) are just a different set of cylinder heads and intake manifold (along with pumps, fuel rails etc).

I've never flown an R22, I did my training on a Bell 47 G2, but the same could be said for retrofitting some of these older aircraft (this Bell was upgraded in it's past to a Lycoming 260 HP engine, I don't remember what the original engine was).
Regards,
Mike

Edited for typo and wording.

[Gaseous]

If a product is that hard to insure perhaps it is an indication it is time to pension it off. Presumably the risk is icing and the potential cost is litigation from victims of carb ice.
Can the R22 be fuel injected? We've done this to death before. Engineering wise an injected R22 would not be a problem. Certification is down to whether Robinson want to do it, and as B73 says, He probably doesnt.

[Bravo73]

Dolmanger,

The FI injected version of the Lycoming 320 block is already available. As heli-mad rightly says, the same engine is already being used in the S300cbi.

However, there is a considerable cost and hassle of certifying a new engine in the old airframe. I don't have the exact numbers but if you are lucky, try asking Robinson who much it cost them to certify the R44 RavenII. (ie essentially a FI Lycoming 540 into the Raven airframe.) But that process made sense - look at the numbers of R44RIIs that they are currently selling.

There might even be the problem of having to re-design the drive train. Although FI doesn't technically give you more power, FI engines do tend to be more powerful. Could the current drive train handle an increase in power? Unlikely.

And then there is the further issue of adding further weight to an aircraft which is already on the limit of it's usable dry empty mass.

So, to my mind, these issues all add up to the R22 either staying carburettored or going out of production. Especially for a company which is currently focusing on squeezing a turbine into a slightly swollen R44 airframe.

[Bravo73]

Can the R22 be fuel injected? We've done this to death before.

Oh, happy days, eh G? ;)

[Bravo73]

Hooloovoo,

Have you tried asking your instructor this question? It would be interesting to hear his/her explanation...


But essentially, the Lycoming block in the R22 is de-rated. ie it is producing very little power for it's capacity. This means that it is hardly stressed at all. Which, in turn, leads to greatly improved reliability.

As far as I'm aware, certain Enstrom models use the same engine (ie Lycoming 320). But in order to supply the power for the increased weight of the aircraft, the engine is turbo-charged. This, in turn, leads to significantly reduced engine reliability.

[ericferret]

Diesels!!!!!!!!!!!!!

[Dolmangar]

Thanks for the answers everyone.

What does a situation like this mean for current owners? Will carb parts become an issue for Robinson owners if the company the makes the parts stops making them? Would they sell the rights to do this?


From my own experience with the 47, I know that often parts can be difficult to secure, and ofcourse you are often purchasing used parts with time remaining instead of new parts. You expect this with an airframe as old as the Bell 47 (but I often see posts about this for more commercial machines being grounded due to lack of spares).


I'll make the assumption that there are companies that remanufacture carbs, similar to alternators, brakes etc in the automotive world.

-Mike

[lars1]

It is not about increasing power. It is about making it more safe for the pilots. When raven 2 was certified I guess the biggest challenge for robinson was to prove that the chassi and drivetrain could withstand the increased power. -Not the FI part

[heli-mad]

From a technical point of view i will agree with B73 about the R22 engine and i will add....
At sea level the engine is capable of producing more power than the transmission and rotor system can safely handle, and to ensure maximum engine and transmission life the O360 must be de-rated, or operated at less than maximum power. As the air becomes thinner with increasing altitude, engine performance decreases, and the pilot can open the throttle to compensate. By derating the engine at sea level, the R22 achieves acceptable high-altitude performance without use of supercharging or turbocharging, thus saving weight and lowering cost.:ok:
the f.i. would add some weight to the 22 and as B73 said being such a light aircraft its not beneficial. The 44 is a different story been bigger with reasonable T.T.O.M for its size.
My personal opinion(strech the personal bit) flying robos for a few years is that the possibility of having a f.i R22 is great but i dont believe it will ever happen. Bear in mind Frank's original idea.....a cheap,light utility helicopter for everybody.
It would be nice to see though a fresh approach to a hugely successful company and with the Raven II outselling everything else out there why not do something similar with the 22....the debate is open:):)
H-M

[rotorfossil]

I once read that an engineer said that if aero engines had originally been fitted with fuel injection and then someone had come along saying that he had designed a hydro mechanical device for supplying fuel and air to an engine in the right ratios and it only had one moving part (ie a carburettor), he would have been hailed as a genius. The carb ice problem is solveable and has been done on non certified fixed wing types with an electric heater device that the pilot doesn't have to control. Why do we go for the complex and heavier fuel injection?

[Gaseous]

Hi B73, Happy days indeed - and it looks like we're doing it all over again.

Fuel injection would add very little weight - in the order of literally a couple of pounds, the extra significant components being the 2 fuel pumps. The servo is not greatly different in weight to the carb and might actually be lighter. (anyone got the actual weights handy?) The power output is determined by the manifold pressure limitation as is the case with the carburettor version so the transmissions ability to handle it is a non issue - not that its likely to be anywhere near its loading limit as applied.

The cost of initial installation in proportion to the cost of the helicopter would be modest. (Based on the cost of replacing it on an Enstrom.)
If you want to see an injection installation which could be applied to the Robinson one needs look no further than the Enstrom non turbo models which use a Lycoming 360 with injection. My aircraft is in for its annual at the same place as an R22 beta2 is being done. I will take some pictures to show how similar they are at the weekend. I'll post them up. Judge for yourself then.

The cost and effort of global re-certification and Frank's desire to do it are the limiting factors. I guess he would rather sell you a Raven 2. Frank was at one time happy to move from a 320 to a 360 for the beta2. A far bigger change than applying injection. If he really wanted, injection could be substituted as it was on the Astro.

Hooloovoo.

The Lyco is inefficient as applied in the Robbie as it runs on the wrong side of the mixture curve. 1/3 of the fuel is wasted.
lt is quite possible to run a Lycoming with injection in an extremely efficient manner. Much has been written here and elsewhere on that by myself and others.
You are correct. Most of the time your car produces very little power and in actual fact its specific fuel consumption will be worse than a Lycoming. Specific fuel consumption is a good measure of efficiency as it is a measure of weight of fuel used per horsepower per hour. The Lycoming can be made pretty damn good- even in comparison to modern gasoline engines.

Rotorfossil. Injection is neither heavy nor complex as applied by Bendix. In fact it is positively crude. It does have one advantage though. No ice. Oh, and its dead reliable.

Ericferret shouts diesels!!!!!.
He may be right ultimately but last time I checked the power to weight of the SMA diesel was inferior to the good ol Lycosaurus. I'm sure someone will do it sooner or later with a diesel - but it wont be an R22.


Edit : I forgot to mention that the 5 minute rating is to keep the temps acceptable and keep Franks (rightly) prized reliability. Nothing to do with the transmission.

[Backward Blade]

Know your machine and it's limitations, do your HASEL check after translation and you won't forget the carb heat...hence no problem.

[mini]

Surely it would be up to Lycoming rather than Robinson to certify a new fuel injected engine? ie the major cost would fall on them - in the first instance?

[Gaseous]

Mini.
No, the engine is almost certainly available already 'off the shelf'. The application needs certification which is down to Robinson. As I have mentioned before the HIO360C1A is pretty much a straight swap for a beta 2, if a little over powerful. Easy to derate by drawing a line on the MAP gauge though.
It still aint going to happen though.

[remote hook]

So, the shampoo works???

Ohhhhhh, you said "carbs....." My mistake, carry on.:p


RH

[ericferret]

Hi Gaseous

The Wilksch engine gives 133hp max continuous from 153 pounds equipped.
1.15 pound per hp.

A 150 hp Lycoming weighs about 250lbs plus equipped.
1.6 pounds per hp.

I would say that even allowing for variation in equipment the diesel comes in better and so it should, being a modern design.
All they have to do is get it to work and they are succeeding.

If the weight difference was only 50 pounds that is a lot in R22 terms.

[Jeff Hall]

For some reason I keep thinking the SMA Diesel would be an ideal project for the R44 Astro / Raven I.

230(ish) HP from a turbo charged 4 cylinder in the space of the 6 cylinder lycoming.

Surely there would be a proper weight benefit to be had?

The actual mechanics could be problematic given the size difference, as would I imagine getting the correlator and governor to work but I'd have thought the diesel's greater torque output would mean less throttle twisting (Manually or by the governor) anyway?

An R44 burning Jet-A1 but without the overhaul costs of the R66 Turbine - Surely thats where Frank ought to be going?

[ericferret]

I really like the Wilksch because it is the only engine that is direct drive like a Lycoming.

The others have reduction gearboxs. This might not be such an issue for helicopters as the reduction could be built into the main gearbox.

The real problem at the moment is that no one is really sure which of the diesels will become the "choice".

The situation is similar to the VHS v BETAMAX fight for the video market. The best system lost out. This is something you do not want to happen in an aircraft engine.

[Gaseous]

Hi Ericferret.
Your comparison is OK for the R22 application and I'm sure you are right. someone will do it. Diesels could well be a replacement for the lower powered Lycoming but the higher performance models are more of a problem.
My figures are based on looking for a replacement for the 225BHP HIO360D1A which has a p/w ratio of about 1.1 if I recall correctly. Last time I looked into it the SMA was the only possibility in terms of power but is too damned heavy.
An interesting thread from the Pprune archive on diesel helicopters is at:
http://www.pprune.org/forums/archive/index.php/t-119279.html

[ericferret]

I think your figures for the HIO 360 D1A might be a little optimistic.
I have it at 190hp from 325 pounds equipped.

A ratio of about 1 to 1.6 pounds.

However that doesn't alter the problem of getting a diesel with about 200hp at a reasonable weight.

Wilksch on their website believe they can develop a 5 cylinder version of their current diesel giving 200hp.

At the current power to weight of 1 to 1.15 that would equate to about 230lbs.
Call it 275lbs and you have at least a 50 lb advantage over the HIO 360.

The down side is that this engine is just a pipedream at the moment.

[Gaseous]

Eric
Yep, youre right. Wrong engine. Wrong helicopter. Its the Enstrom HIO360F1AD thats 225bhp.I was probably was comparing dry with no accessories.
The memory's going and it was 2002 we did this last time. Excuses over.
Even so the weight penalty for an aircraft using the SMA instead of a Lycoming is about 125lbs. Dont forget diesel and jeta1 are heavier than avgas too.
Edit: SMA quote the 'dry' weight at a gutbusting 430lbs. Lyco 293lbs.